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Diffstat (limited to 'Documentation/btrfs-mount.asciidoc')
| -rw-r--r-- | Documentation/btrfs-mount.asciidoc | 270 |
1 files changed, 135 insertions, 135 deletions
diff --git a/Documentation/btrfs-mount.asciidoc b/Documentation/btrfs-mount.asciidoc index d364594f..3fc4ccbd 100644 --- a/Documentation/btrfs-mount.asciidoc +++ b/Documentation/btrfs-mount.asciidoc @@ -14,215 +14,215 @@ Other generic mount options are available,and are described in the MOUNT OPTIONS ------------- *alloc_start='bytes'*:: - Debugging option to force all block allocations above a certain - byte threshold on each block device. The value is specified in - bytes, optionally with a K, M, or G suffix, case insensitive. - Default is 1MB. +Debugging option to force all block allocations above a certain +byte threshold on each block device. The value is specified in +bytes, optionally with a K, M, or G suffix, case insensitive. +Default is 1MB. *autodefrag*:: *noautodefrag*:: - (since: 3.0, default: off) + - Disable/enable auto defragmentation. - Auto defragmentation detects small random writes into files and queue - them up for the defrag process. Works best for small files; - Not well suited for large database workloads. - + - WARNING: Defragmenting with Linux kernel versions < 3.9 or ≥ 3.14-rc2 as - well as with Linux stable kernel versions ≥ 3.10.31, ≥ 3.12.12 or - ≥ 3.13.4 will break up the ref-links of CoW data (for example files - copied with `cp --reflink`, snapshots or de-duplicated data). - This may cause considerable increase of space usage depending on the - broken up ref-links. +(since: 3.0, default: off) + +Disable/enable auto defragmentation. +Auto defragmentation detects small random writes into files and queue +them up for the defrag process. Works best for small files; +Not well suited for large database workloads. ++ +WARNING: Defragmenting with Linux kernel versions < 3.9 or ≥ 3.14-rc2 as +well as with Linux stable kernel versions ≥ 3.10.31, ≥ 3.12.12 or +≥ 3.13.4 will break up the ref-links of CoW data (for example files +copied with `cp --reflink`, snapshots or de-duplicated data). +This may cause considerable increase of space usage depending on the +broken up ref-links. *check_int*:: *check_int_data*:: *check_int_print_mask='value'*:: - (since: 3.0, default: off) + - These debugging options control the behavior of the integrity checking - module (the BTRFS_FS_CHECK_INTEGRITY config option required). + - + - `check_int` enables the integrity checker module, which examines all - block write requests to ensure on-disk consistency, at a large - memory and CPU cost. + - + - `check_int_data` includes extent data in the integrity checks, and - implies the check_int option. + - + - `check_int_print_mask` takes a bitmask of BTRFSIC_PRINT_MASK_* values - as defined in 'fs/btrfs/check-integrity.c', to control the integrity - checker module behavior. + - + - See comments at the top of 'fs/btrfs/check-integrity.c' - for more info. +(since: 3.0, default: off) + +These debugging options control the behavior of the integrity checking +module (the BTRFS_FS_CHECK_INTEGRITY config option required). + ++ +`check_int` enables the integrity checker module, which examines all +block write requests to ensure on-disk consistency, at a large +memory and CPU cost. + ++ +`check_int_data` includes extent data in the integrity checks, and +implies the check_int option. + ++ +`check_int_print_mask` takes a bitmask of BTRFSIC_PRINT_MASK_* values +as defined in 'fs/btrfs/check-integrity.c', to control the integrity +checker module behavior. + ++ +See comments at the top of 'fs/btrfs/check-integrity.c' +for more info. *commit='seconds'*:: - (since: 3.12, default: 30) + - Set the interval of periodic commit. Higher - values defer data being synced to permanent storage with obvious - consequences when the system crashes. The upper bound is not forced, - but a warning is printed if it's more than 300 seconds (5 minutes). +(since: 3.12, default: 30) + +Set the interval of periodic commit. Higher +values defer data being synced to permanent storage with obvious +consequences when the system crashes. The upper bound is not forced, +but a warning is printed if it's more than 300 seconds (5 minutes). *compress*:: *compress='type'*:: *compress-force*:: *compress-force='type'*:: - (default: off) + - Control BTRFS file data compression. Type may be specified as 'zlib', - 'lzo' or 'no' (for no compression, used for remounting). If no type - is specified, 'zlib' is used. If compress-force is specified, - all files will be compressed, whether or not they compress well. - NOTE: If compression is enabled, 'nodatacow' and 'nodatasum' are disabled. +(default: off) + +Control BTRFS file data compression. Type may be specified as 'zlib', +'lzo' or 'no' (for no compression, used for remounting). If no type +is specified, 'zlib' is used. If compress-force is specified, +all files will be compressed, whether or not they compress well. +NOTE: If compression is enabled, 'nodatacow' and 'nodatasum' are disabled. *degraded*:: - (default: off) + - Allow mounts to continue with missing devices. A read-write mount may - fail with too many devices missing, for example if a stripe member - is completely missing. +(default: off) + +Allow mounts to continue with missing devices. A read-write mount may +fail with too many devices missing, for example if a stripe member +is completely missing. *device='devicepath'*:: - Specify a device during mount so that ioctls on the control device - can be avoided. Especially useful when trying to mount a multi-device - setup as root. May be specified multiple times for multiple devices. +Specify a device during mount so that ioctls on the control device +can be avoided. Especially useful when trying to mount a multi-device +setup as root. May be specified multiple times for multiple devices. *discard*:: *nodiscard*:: - (default: off) + - Disable/enable discard mount option. - Discard issues frequent commands to let the block device reclaim space - freed by the filesystem. - This is useful for SSD devices, thinly provisioned - LUNs and virtual machine images, but may have a significant - performance impact. (The fstrim command is also available to - initiate batch trims from userspace). +(default: off) + +Disable/enable discard mount option. +Discard issues frequent commands to let the block device reclaim space +freed by the filesystem. +This is useful for SSD devices, thinly provisioned +LUNs and virtual machine images, but may have a significant +performance impact. (The fstrim command is also available to +initiate batch trims from userspace). *enospc_debug*:: - (default: off) + - Disable/enable debugging option to be more verbose in some ENOSPC conditions. +(default: off) + +Disable/enable debugging option to be more verbose in some ENOSPC conditions. *fatal_errors='action'*:: - (since: 3.4, default: bug) + - Action to take when encountering a fatal error. + - "bug" - BUG() on a fatal error. + - "panic" - panic() on a fatal error. +(since: 3.4, default: bug) + +Action to take when encountering a fatal error. + + "bug" - BUG() on a fatal error. + + "panic" - panic() on a fatal error. *flushoncommit*:: *noflushoncommit*:: - (default: on) + - The `flushoncommit` mount option forces any data dirtied by a write in a - prior transaction to commit as part of the current commit. This makes - the committed state a fully consistent view of the file system from the - application's perspective (i.e., it includes all completed file system - operations). This was previously the behavior only when a snapshot is - created. +(default: on) + +The `flushoncommit` mount option forces any data dirtied by a write in a +prior transaction to commit as part of the current commit. This makes +the committed state a fully consistent view of the file system from the +application's perspective (i.e., it includes all completed file system +operations). This was previously the behavior only when a snapshot is +created. *inode_cache*:: *noinode_cache*:: - (since: 3.0, default: off) + - Enable free inode number caching. Defaults to off due to an overflow - problem when the free space crcs don't fit inside a single page. +(since: 3.0, default: off) + +Enable free inode number caching. Defaults to off due to an overflow +problem when the free space crcs don't fit inside a single page. *max_inline='bytes'*:: - (default: min(8192, page size) ) - Specify the maximum amount of space, in bytes, that can be inlined in - a metadata B-tree leaf. The value is specified in bytes, optionally - with a K, M, or G suffix, case insensitive. In practice, this value - is limited by the root sector size, with some space unavailable due - to leaf headers. For a 4k sectorsize, max inline data is ~3900 bytes. +(default: min(8192, page size) ) +Specify the maximum amount of space, in bytes, that can be inlined in +a metadata B-tree leaf. The value is specified in bytes, optionally +with a K, M, or G suffix, case insensitive. In practice, this value +is limited by the root sector size, with some space unavailable due +to leaf headers. For a 4k sectorsize, max inline data is ~3900 bytes. *metadata_ratio='value'*:: - Specify that 1 metadata chunk should be allocated after every - 'value' data chunks. Off by default. +Specify that 1 metadata chunk should be allocated after every +'value' data chunks. Off by default. *acl*:: *noacl*:: - (default: on) + - Enable/disable support for Posix Access Control Lists (ACLs). See the - `acl`(5) manual page for more information about ACLs. +(default: on) + +Enable/disable support for Posix Access Control Lists (ACLs). See the +`acl`(5) manual page for more information about ACLs. *barrier*:: *nobarrier*:: - (default: on) + - ensure that certain IOs make it through the device cache and are on - persistent storage. If disabled on a device with a volatile - (non-battery-backed) write-back cache, nobarrier option will lead to - filesystem corruption on a system crash or power loss. +(default: on) + +ensure that certain IOs make it through the device cache and are on +persistent storage. If disabled on a device with a volatile +(non-battery-backed) write-back cache, nobarrier option will lead to +filesystem corruption on a system crash or power loss. *datacow*:: *nodatacow*:: - (default: on) + - Enable/disable data copy-on-write for newly created files. - Nodatacow implies nodatasum, and disables all compression. +(default: on) + +Enable/disable data copy-on-write for newly created files. +Nodatacow implies nodatasum, and disables all compression. *datasum*:: *nodatasum*:: - (default: on) + - Enable/disable data checksumming for newly created files. - Datasum implies datacow. +(default: on) + +Enable/disable data checksumming for newly created files. +Datasum implies datacow. *treelog*:: *notreelog*:: - (default: on) + - Enable/disable the tree logging used for fsync and O_SYNC writes. +(default: on) + +Enable/disable the tree logging used for fsync and O_SYNC writes. *recovery*:: - (since: 3.2, default: off) + - Enable autorecovery attempts if a bad tree root is found at mount time. - Currently this scans a list of several previous tree roots and tries to - use the first readable. +(since: 3.2, default: off) + +Enable autorecovery attempts if a bad tree root is found at mount time. +Currently this scans a list of several previous tree roots and tries to +use the first readable. *rescan_uuid_tree*:: - (since: 3.12, default: off) + - Force check and rebuild procedure of the UUID tree. This should not - normally be needed. +(since: 3.12, default: off) + +Force check and rebuild procedure of the UUID tree. This should not +normally be needed. *skip_balance*:: - (since: 3.3, default: off) + - Skip automatic resume of interrupted balance operation after mount. - May be resumed with "btrfs balance resume." +(since: 3.3, default: off) + +Skip automatic resume of interrupted balance operation after mount. +May be resumed with "btrfs balance resume." *nospace_cache*:: - (since: 3.2) + - Disable freespace cache loading without clearing the cache. +(since: 3.2) + +Disable freespace cache loading without clearing the cache. *clear_cache*:: - Force clearing and rebuilding of the disk space cache if something - has gone wrong. +Force clearing and rebuilding of the disk space cache if something +has gone wrong. *ssd*:: *nossd*:: *ssd_spread*:: - Options to control ssd allocation schemes. By default, BTRFS will - enable or disable ssd allocation heuristics depending on whether a - rotational or nonrotational disk is in use. The ssd and nossd options - can override this autodetection. + - The ssd_spread mount option attempts to allocate into big chunks - of unused space, and may perform better on low-end ssds. ssd_spread - implies ssd, enabling all other ssd heuristics as well. +Options to control ssd allocation schemes. By default, BTRFS will +enable or disable ssd allocation heuristics depending on whether a +rotational or nonrotational disk is in use. The ssd and nossd options +can override this autodetection. + +The ssd_spread mount option attempts to allocate into big chunks +of unused space, and may perform better on low-end ssds. ssd_spread +implies ssd, enabling all other ssd heuristics as well. *subvol='path'*:: - Mount subvolume at 'path' rather than the root subvolume. The - 'path' is relative to the top level subvolume. +Mount subvolume at 'path' rather than the root subvolume. The +'path' is relative to the top level subvolume. *subvolid='ID'*:: - Mount subvolume specified by an ID number rather than the root subvolume. - This allows mounting of subvolumes which are not in the root of the mounted - filesystem. - You can use "btrfs subvolume list" to see subvolume ID numbers. +Mount subvolume specified by an ID number rather than the root subvolume. +This allows mounting of subvolumes which are not in the root of the mounted +filesystem. +You can use "btrfs subvolume list" to see subvolume ID numbers. *subvolrootid='objectid'*:: - (deprecated) + - Mount subvolume specified by 'objectid' rather than the root subvolume. - This allows mounting of subvolumes which are not in the root of the mounted - filesystem. - You can use "btrfs subvolume show" to see the object ID for a subvolume. +(deprecated) + +Mount subvolume specified by 'objectid' rather than the root subvolume. +This allows mounting of subvolumes which are not in the root of the mounted +filesystem. +You can use "btrfs subvolume show" to see the object ID for a subvolume. *thread_pool='number'*:: - The number of worker threads to allocate. The default number is equal - to the number of CPUs + 2, or 8, whichever is smaller. +The number of worker threads to allocate. The default number is equal +to the number of CPUs + 2, or 8, whichever is smaller. *user_subvol_rm_allowed*:: - (default: off) + - Allow subvolumes to be deleted by a non-root user. Use with caution. +(default: off) + +Allow subvolumes to be deleted by a non-root user. Use with caution. FILE ATTRIBUTES --------------- |